1. Field of the Invention
The present invention relates to an improvement of an image stabilizing device for a camera, capable of preventing an image blur caused by a hand shake (or vibration).
2. Related Background Art
Various types of conventional image blur compensation devices have been proposed, as disclosed in Japanese Laid-Open Patent Application No. 63-49729.
In order to prevent an image blur on a focusing plane, which blur is originated by a hand vibration, an optical axis eccentric means as a target control object is moved by a feedback control mechanism to suppress the image blur.
For example, a hand vibration (normally an oblique vibration of a camera with respect to a photographic optical axis) of the camera is detected as an acceleration signal, the acceleration signal is integrated by a signal processing system to obtain a velocity signal (and then a deviation signal), and the optical axis eccentric means is driven in a direction to suppress the camera vibration (i.e., a direction to suppress the image blur).
FIG. 25 shows a basic arrangement of an image blur compensation device including the above signal processing system. The image blur compensation device includes an acceleration detector 101 for detecting an oblique movement of a camera (not shown) with respect to the photographic optical axis of the camera as an acceleration signal a. The detected acceleration signal a is integrated into a velocity signal v by a first integrator 102. The velocity signal v is converted into a deviation signal d by a second integrator 103.
An actuator 105 is operated to drive a radially movable optical axis eccentric means 104 (normally a focusing lens system) of the camera in accordance with the deviation signal d.
A position sensor 106 constitutes a position detecting means for detecting an actual deviation of the optical axis eccentric means 104. A signal from the position sensor 106 is fed back to an input system of the actuator 105 through an operational amplifier 107, thereby forming a feedback loop for causing driving control to correspond to the vibration deviation.
On the other hand, various proposals have been made for photometry systems and autofocus (AF) systems for cameras.
Known photometry systems are a system having an average photometry mode for performing uniform photometry on the entire frame, a system having a spot photometry mode for performing photometry of only the central portion of the frame, and a system having an evaluative photometry mode for performing photometry with optimal weighting on the basis of conditions such as a back light state and a main object position.
When the image blur compensation device is combined with the above photometry modes, their effects cannot often be sufficiently enhanced.
More specifically, in the spot photometry mode, a photographer or user usually performs spot photometry of a main object and retries framing to obtain a desired frame. At this time, when an image blur compensation function mode is set, the compensation function is effected because a slight change in framing is detected as a hand vibration. As a result, current framing cannot be changed, or a desired frame cannot be obtained.
The following AF modes are proposed for the above AF system:
1) One-shot AF (or single AF): AF inhibited once an in-focus state is obtained; PA1 2) Servo AF (or continuous AF): AF performed repeatedly; and PA1 3) Moving object anticipation servo AF: AF performed to compensate for an AF tracking delay occurring in a high-speed moving object during a release operation during an AF operation. PA1 1) Since a stationary object is often focused in the one-shot AF mode, a hand vibration is generally discriminated in this mode. PA1 2) Since an irregularly moving object is traced in the servo AF mode, a change in framing is large. PA1 3) Since an object moving in one direction is focused in a moving object anticipation servo AF mode, a camera movement is one-directional camera movement, i.e., panning.
However, when the image blur compensation device is combined with an autofocus device (AF device), and this combination is applied to a camera or the like, the effect of the combination cannot often be sufficiently enhanced. In order to distinguish a hand vibration of a photographer from panning or a change in framing in the image blur compensation device, types of blurs are classified to estimate a photographer's intention. Processing such as a change in blur compensation range is performed on the basis of this estimation, thereby improving operability.
When a camera having a plurality of AF modes is used in a given AF mode, framing unique to the given AF mode is often performed. For example, the following operations may be assumed.
In the conventional arrangement, blur actions in the above AF modes are not estimated, and the photographer's intention is estimated from only a blur signal. As a result, the conventional arrangement is not necessarily convenient.
Many applications relating to AF devices and autoexposure (AE) devices have been made. Of these applications, there is provided a device utilizing the AF and AE devices to determine focus and aperture states so that a plurality of different objects are focused. For example, in Japanese Laid-Open Patent Application No. 63-85722 filed by the present applicant, a photographic lens is shifted to focus an object at the first distance by an AF device, and focus detection is performed for an object at the second distance. A defocus amount at the second distance with respect to the first distance is obtained, and an aperture value and a focus position are obtained so that the first and second objects are set in the in-focus state. The focus control lens position and the aperture value are controlled on the basis of the operation result, and photographing is performed. A photograph focused on both the objects at different distances can be obtained. This exposure control mode is called a depth priority AE mode.
When the image blur compensation device is used in combination with the depth priority AE mode, their effects cannot often be sufficiently enhanced.
When many functions such as image blur compensation, focus control, and exposure control are automated, it is important to determine the first operation of each function in consideration of the operability of the camera. In general, each function is selected in an automatic or manual mode, and then one operation member such as a switch turned on upon depression of, e.g., a release button to the half stroke is used as a trigger switch for starting all the functions. However, in the depth priority mode, at least two focus detection operations are performed in the depth priority mode, and a change in framing is performed every detection. An image blur detector in the image blur compensation device detects a change in framing as a large blur. A large deviation signal is generated in the blur detector after a change in framing occurs. When the release button is depressed to perform focus detection in this state, the image blur compensation device is operated. Accurate image blur compensation cannot be performed by the large deviation signal in the image blur detector. In addition, an object cannot be caught within the focus detection frame due to an abnormal behavior of the image blur compensation mechanism. Therefore, accurate focus detection cannot be performed.